I purchased a set of Black Widow castings from Dwight Giles during the 2012 Portland Gears Model Show. The documentation was a disaster, and after several phone conversations with Dwight I realized I'd need a lot more engine building experience before even thinking about tackling it. Still in their original shipping box, the castings were moved into my attic and in the intervening years twice offered for sale with no takers.
After finishing the 289 HiPo I began looking for another challenging project, and the castings were hauled down from the attic. Initially I wasn't enthusiastic about starting another V8 build, but the blower would be a new twist and something I could get interested in. I'm not sure how functional it was intended to be, but I'd already begun thinking about how I'd tackle a set of close fitting rotors. Ironically my documentation doesn't include any information on the blower.
Looking ahead, I'll likely include an electric starter similar to the one on the 289 which has been working well. I'm not yet sure about carburetion. There's nothing about a carburetor in my documentation, but a large colored poster that was in the box with the castings shows the engine sporting a pair of mystery Walbros. Also, with practically no documentation on the oil or water pumps, I haven't yet decided if there will be an oil pump, but the engine will definitely be water cooled. The camshaft will probably be a roller with the 289's profile, but with a slightly earlier exhaust valve opening. The immediate goal however is to focus on a foundational assembly of the block, heads, and intake manifold. With this in hand, a crank and camshaft will be designed to fit.
Chip making started with the rough machining of the block, head, and manifold castings to create a starting set of dimensions for their machined surfaces and features. Beginning with the block's pan surface, the absolute minimum amount of material was removed from each casting to obtain true and symmetrical mating surfaces. The 13 year-old age-hardened castings machined very nicely with only minor porosities showing up on the block decks. Dimensions of the oversize machined castings were carefully taken and used to construct SolidWorks (2010) models which were in turn used to create a virtual assembly.
Using the supplied drawings as a starting point, the cylinders and lifter bores and head bolts were located with respect to centerlines positioned on the oversized models. Centerline referencing allowed the features to be located on the models before they were brought to their finished sizes. The row of lifter bores which are immediately adjacent to the block's un-machined inner deck walls were used to construct the longitudinal centerlines in each bank to locate one axis of the drilled features. For the second axis a single orthogonal centerline for both banks was constructed in the middle of the un-machined web for the center main bearing. This centerline located the cylinder bores, lifter bores and the head bolts in both banks with the port bank features offset .156" behind it, and the starboard bank features offset .156" in front of it. The cylinder bores in each bank are 1.625" apart, and there is a .3125" offset between banks. There's .3125" between the lifters in each cylinder's pair, and each pair is centered over its cylinder.
A front cross-sectional view of the virtual assembly was monitored to ensure a vertical cam-crank separation of 1.405" inches to guarantee the engine's timing gear spacing. In my case it showed there was still .3425" excess material to be removed from the block's pan surface. Compared with the other surfaces this was a lot, and so it will be put off until the bore for the camshaft is drilled. This view also verified the locations of cylinder and lifter bore axes which must intersect the axes of the crankshaft and camshaft bores, respectively.
According to my documentation, a single head with identically located features was expected to be used on both banks. In my case the offset features between banks caused one of these heads to come up short of the block's front surface and leave a tiny gap. To avoid this I created unique port and starboard heads whose feature are offset from each other by .125". Hopefully this won't create problems with the yet to be located fuel, water and oil passages. They'll be modeled before any drilling is done.
A virtual model of the intake manifold was also created using the dimensions of the actual oversized machined manifold. Of the four castings, the intake manifold was the most difficult to accurately machine. Its ends were machined parallel to each other before its bottom and top surfaces were faced parallel. The two 45 degree surfaces were the most critical and were done in a couple iterations using small cuts. The virtual intake was spaced off the block and heads by .030" to account for the head and manifold gaskets.
Dowel pins were then added to the virtual block and heads and then machined into the actual castings. Both heads have identical dowel locations which may prove to be a mistake, but I thought doing so would simplify fixturing later on. A set of .030" shims added to the actual assembly allowed a continual comparison between it and the virtual assembly as it was being finish machined. The decks were left with .005" excess stock for a clean-up pass after the liners are installed.
For a final sanity check, the block was set up in the mill and each bank indicated on its dowel pins. A quarter inch test bar in the spindle verified the (.015") clearances between the un-machined inner walls of the block and the locations where the lifters are to be bored.
The next steps will include the final machining of the block's pan surface so the 7" deep camshaft bore can be drilled. The oil and water holes will also be located before any of the other features are drilled. - Terry
After finishing the 289 HiPo I began looking for another challenging project, and the castings were hauled down from the attic. Initially I wasn't enthusiastic about starting another V8 build, but the blower would be a new twist and something I could get interested in. I'm not sure how functional it was intended to be, but I'd already begun thinking about how I'd tackle a set of close fitting rotors. Ironically my documentation doesn't include any information on the blower.
Looking ahead, I'll likely include an electric starter similar to the one on the 289 which has been working well. I'm not yet sure about carburetion. There's nothing about a carburetor in my documentation, but a large colored poster that was in the box with the castings shows the engine sporting a pair of mystery Walbros. Also, with practically no documentation on the oil or water pumps, I haven't yet decided if there will be an oil pump, but the engine will definitely be water cooled. The camshaft will probably be a roller with the 289's profile, but with a slightly earlier exhaust valve opening. The immediate goal however is to focus on a foundational assembly of the block, heads, and intake manifold. With this in hand, a crank and camshaft will be designed to fit.
Chip making started with the rough machining of the block, head, and manifold castings to create a starting set of dimensions for their machined surfaces and features. Beginning with the block's pan surface, the absolute minimum amount of material was removed from each casting to obtain true and symmetrical mating surfaces. The 13 year-old age-hardened castings machined very nicely with only minor porosities showing up on the block decks. Dimensions of the oversize machined castings were carefully taken and used to construct SolidWorks (2010) models which were in turn used to create a virtual assembly.
Using the supplied drawings as a starting point, the cylinders and lifter bores and head bolts were located with respect to centerlines positioned on the oversized models. Centerline referencing allowed the features to be located on the models before they were brought to their finished sizes. The row of lifter bores which are immediately adjacent to the block's un-machined inner deck walls were used to construct the longitudinal centerlines in each bank to locate one axis of the drilled features. For the second axis a single orthogonal centerline for both banks was constructed in the middle of the un-machined web for the center main bearing. This centerline located the cylinder bores, lifter bores and the head bolts in both banks with the port bank features offset .156" behind it, and the starboard bank features offset .156" in front of it. The cylinder bores in each bank are 1.625" apart, and there is a .3125" offset between banks. There's .3125" between the lifters in each cylinder's pair, and each pair is centered over its cylinder.
A front cross-sectional view of the virtual assembly was monitored to ensure a vertical cam-crank separation of 1.405" inches to guarantee the engine's timing gear spacing. In my case it showed there was still .3425" excess material to be removed from the block's pan surface. Compared with the other surfaces this was a lot, and so it will be put off until the bore for the camshaft is drilled. This view also verified the locations of cylinder and lifter bore axes which must intersect the axes of the crankshaft and camshaft bores, respectively.
According to my documentation, a single head with identically located features was expected to be used on both banks. In my case the offset features between banks caused one of these heads to come up short of the block's front surface and leave a tiny gap. To avoid this I created unique port and starboard heads whose feature are offset from each other by .125". Hopefully this won't create problems with the yet to be located fuel, water and oil passages. They'll be modeled before any drilling is done.
A virtual model of the intake manifold was also created using the dimensions of the actual oversized machined manifold. Of the four castings, the intake manifold was the most difficult to accurately machine. Its ends were machined parallel to each other before its bottom and top surfaces were faced parallel. The two 45 degree surfaces were the most critical and were done in a couple iterations using small cuts. The virtual intake was spaced off the block and heads by .030" to account for the head and manifold gaskets.
Dowel pins were then added to the virtual block and heads and then machined into the actual castings. Both heads have identical dowel locations which may prove to be a mistake, but I thought doing so would simplify fixturing later on. A set of .030" shims added to the actual assembly allowed a continual comparison between it and the virtual assembly as it was being finish machined. The decks were left with .005" excess stock for a clean-up pass after the liners are installed.
For a final sanity check, the block was set up in the mill and each bank indicated on its dowel pins. A quarter inch test bar in the spindle verified the (.015") clearances between the un-machined inner walls of the block and the locations where the lifters are to be bored.
The next steps will include the final machining of the block's pan surface so the 7" deep camshaft bore can be drilled. The oil and water holes will also be located before any of the other features are drilled. - Terry
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